1010-3-3 Composite Figures - Neshaminy School District

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Warm Up Lesson Presentation Lesson Quiz

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10-3 Composite Figures

Warm Up Find the area of each figure.

1. a rectangle in which b = 14 cm and h = 5 cm A = 70 cm2

2. a triangle in which b = 6 in. and h = 18 in. A = 54 in2

3. a trapezoid in which b1 = 7 ft, b2 = 11 ft, and h = 3 ft A = 27 ft2

Holt McDougal Geometry

10-3 Composite Figures

Objectives

Use the Area Addition Postulate to find the areas of composite figures. Use composite figures to estimate the areas of irregular shapes.

Holt McDougal Geometry

10-3 Composite Figures

Vocabulary

composite figure

Holt McDougal Geometry

10-3 Composite Figures

A composite figure is made up of simple shapes, such as triangles, rectangles, trapezoids, and circles. To find the area of a composite figure, find the areas of the simple shapes and then use the Area Addition Postulate.

Holt McDougal Geometry

10-3 Composite Figures

Example 1A: Finding the Areas of Composite Figures by Adding

Find the shaded area. Round to the nearest tenth, if necessary.

Divide the figure into parts.

area of half circle:

Holt McDougal Geometry

10-3 Composite Figures

Example 1A Continued

area of triangle:

Holt McDougal Geometry

area of the rectangle: A = bh = 20(14) = 280 mm2

shaded area:

50 + 280 + 84 521.1 mm2

10-3 Composite Figures

Example 1B: Finding the Areas of Composite Figures by Adding

Find the shaded area. Round to the nearest tenth, if necessary.

Divide the figure into parts.

area of parallelogram: A = bh = 8(5)= 40ft2

area of triangle:

Holt McDougal Geometry

shaded area: 40 + 25 = 65 ft2

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